This application relates to techniques, apparatus and systems that use optical waveguides to deliver light to a targeted area for optical detection of tissues, organs and other objects in medical, biological and other applications.
Light can be guided through a light pipe or optical waveguide such as optic fiber to a target to obtain optical images, optical measurements and other operations of the target. The optical waveguide such as optic fiber can be used to reach the target at a location that is otherwise difficult to reach or requires some preparatory procedures to make the target more accessible. For example, the tissue of an internal organ of a patient may be made available for a medical examination or therapy procedure through a natural orifice or an incision to expose the internal organ. Such a procedure may be performed by delivering probe light to the tissue via an endoscope instrument or catheter to reduce or minimize the degree of invasiveness of a diagnostic or therapeutic procedure. At the distal end of the instrument, light is pointed to certain direction or steered to interact with an area or a slice of tissue of interest.
Various devices and techniques based on optical coherence domain reflectometry (OCDR) may be used for non-invasive optical probing of various substances, including but not limited to skins, body tissues and organs of humans and animals, to provide tomographic measurements of these substances. In many OCDR systems, the light from a light source is split into a sampling beam and a reference beam which propagate in two separate optical paths, respectively. The light source may be partially coherent source. The sampling beam is directed along its own optical path to impinge on the substances under study, or sample, while the reference beam is directed in a separate path towards a reference surface. The beams reflected from the sample and from the reference surface are then brought to overlap with each other to optically interfere. Because of the wavelength-dependent phase delay, the optical interference results in no observable interference fringes unless the two optical path lengths of the sampling and reference beams are similar. This provides a physical mechanism for ranging. A beam splitter may be used to split the light from the light source and to combine the reflected sampling beam and the reflected reference beam for detection at an optical detector. The application of OCDR in medical diagnoses in certain optical configurations has come to be known as “optical coherence tomography” (OCT).